The microbiome and volatile organic compounds reflecting the state of decomposition in an indoor environment

Abstract

Given that a variety of factors can affect the decomposition process, it can be difficult to determine the post-mortem interval (PMI). The process is highly dependent on microbial activity, and volatile organic compounds (VOCs) are a by-product of this activity. Given both have been proposed to assist in PMI determination, a deeper understanding of this relationship is needed. The current study investigates the temporal evolution of the microbiome and VOC profile of a decomposing human analog (swine) in a controlled, indoor environment. Microbial communities were sampled at six-time points up to the active decay phase (72 swabs in total). VOC headspace samples were collected every six hours with six sampling times in common with the swab times. Sampling locations included the abdominal area, anus, right ear canal, and right nostril. Bacterial communities were found to significantly change during decomposition (p < 0.001), and communities shifted differently based on sample location. The families Moraxellaceae, Planococcaceae, Lactobacillaceae, and Staphylococcaceae drove these community shifts. From random forest analysis, the nostril sampling location was determined to be the best location to predict stage of decomposition. Individual VOCs exhibited large temporal shifts through decomposition stage in contrast to smaller shifts when evaluated based on functional groups. Finally, pairwise linear regression models between abdominal area bacteria and selected VOCs were assessed; Planococcaceae and Tissierellaceae were significantly correlated to indole. Overall, this study provides an exploratory analysis to support the connection between the microbiome, VOCs, and their relationship throughout decomposition.